The present invention relates to meteor burst communication systems, and more particularly to a meteor burst communication system having the capability of simultaneous communication with multiple remote units.
Meteor burst communication systems are becoming well known for providing communication of low data rate packets of digital data between a base station and one or more remote units over long distances, such as up to 1,000 miles or more.
In a typical meteor burst communication system, a base station transmits digital probe signals to one or more remote units. A remote unit receiving a probe signal responds by transmitting a digital data signal to the base station. The signals are reflected from ionization trails left by meteors that are traveling through the Earth""s upper atmosphere at an altitude of about 50 to 70 miles above the Earth""s surface. The meteor trails result from the ionization of air particles through which the meteor travels and exist for only a short time interval, such as from a few milliseconds to a few seconds. Therefore, a signal burst transmission mode is typically used for transmitting the probe signals and data signals. The durations of the signal bursts are selected such that the overall time for their transmission does not exceed the time of duration of a typical meteor ionization trail. Thus, the signal bursts typically range from tens of milliseconds to hundreds of milliseconds.
Meteor burst communication systems are well suited for communicating between stationary transceivers. For example, the meteor burst communication system of U.S. Pat. No. 4,277,845 discloses fixed remote units that transmit weather data from relatively inaccessible regions, where the remote units are located, to a fixed base station.
Meteor burst communication systems are also well suited for communicating between a stationary base station and mobile remote units. For example, a mobile radio communication network uses meteor burst communications to communicate vehicle position data to a base station from remote units that are mounted on the vehicles. Such a system is disclosed in U.S. Pat. No. 4,845,504.
As the number of remote units increases, the geographic area between remote units decreases correspondingly. This results in an increased probability that more than one remote unit will acknowledge a probe signal at about the same time. This can result in a collision between simultaneous transmissions of two remote units.
The prior art dealt with the problem of collisions between simultaneous transmissions by simply avoiding collisions. For example, in U.S. Pat. No. 4,845,504, an attempt is made to avoid collisions between simultaneous transmissions of two mobile stations through the use of a selective antenna receive pattern at the base station. However, in the event that two simultaneous mobile transmissions are received in a same receive sector, the base station will not acknowledge any message containing errors as a result of the collision between simultaneous transmissions.
Therefore, in the prior art, base stations communicate with remote units one at a time in a time-sequential manner. This is an inefficient use of the communication capabilities of a meteor burst communication system and limits the number of remote units that can be serviced by a base station. Therefore, there is an unmet need in the art for a meteor burst communication system having a capability of simultaneously communicating with multiple remote units.
The present invention provides a meteor burst communication system that includes a base station capable of simultaneously communicating with multiple remote units via meteor ionization trails. The base station includes a main processor that generates a probe signal. A transmitter transmits the probe signal throughout a geographic area that includes the remote units. The remote units receive the probe signal and respond by transmitting data signals to the base station. The base station includes a plurality of receivers that receive the data signals from the remote units via the meteor ionization trails. A plurality of receiver processors process the data signals received from the remote units. When all the received data signals have been processed by the plurality of receiver processors, the main processor formulates an acknowledgment signal, and the acknowledgment signal is transmitted throughout the geographic area that includes the remote units.
According to one aspect of the present invention, each receiver is coupled to provide its demodulated output signal to an associated receiver processor. Each receiver processor is coupled to supply its output signal to a main processor. Signals from multiple remote units can be received by the receivers, and each separate receiver processor can process the signals received from the remote units at the same time. Therefore, according to the present invention, the processing capability of the meteor burst base station is increased beyond conventional meteor burst base stations and the base station can communicate with more remote units than can conventional meteor burst base stations.